The invention relates to novel and improved non-woven structures and methods and apparatus for producing such structures and is particularly concerned with bonded non-woven fabrics having a predetermined pattern of spaced bonded area separated by substantially unbonded areas.
Many attempts to produce non-woven fabrics having good handle, drapeability, strength and abrasion resistance are known. Amongst these methods may be mentioned the forming of a homogeneous fibrous web which is then bonded by the application thereto of heat or heat and pressure between platens or nip rollers to cause the fibre to soften and bond with contiguous fibres. The method suffers from the disadvantage that extremely precise control of the bonding operation is required in order to obtain a correctly bonded fabric since if the conditions are not strictly adhered to either a weakly bonded structure with low abrasion resistance and strength is obtained, or else an undrapeable, harsh to handle structure caused by the substantial loss of fibrous form is obtained.
An improved method of bonding is to impregnate the fibrous web with suitable adhesives, gum, resins and the like. Whilst the strength and abrasion resistance are undoubtedly improved, the bonded fabric so obtained has poor drapeability and harsh handle because of the uncontrollable spread of adhesive throughout the structure. It is also known to incorporate the binding medium in fibrous form (in addition to non-binder fibres) in non-woven fabrics and to submit such fabrics to a treatment to render the binder fibres adhesive whilst leaving all other non-binder fibres unaffected, thus bonding the fibres of the fabric together. However, the fabrics bonded by such a method similarly have poor drapeability and a harsh handle caused by loss of fibrous form of the binder fibres when subjected to the bonding process with consequent spread of the binder throughout the fabric.
The drape and handle of bonded non-woven fabrics can be somewhat improved if the fabrics although completely bonded are produced with regions which are less strongly bonded than are other regions. Thus, in a bonding process utilizing heat and pressure, if at least one of the rollers applying pressure to the non-woven structure has a patterned surface, a bonded fabric of fairly good drape and handle will be obtained, since the fabrics bonded by the use of such rollers have regions which are less strongly bonded than others, the more strongly bonded regions being the result of direct contact between the parts of the pattern in relief and the fabric, and the less strongly bonded regions being the result of heat radiation from the other parts of the roller which are not in contact with the fabric. However, the overall bonding i.e. the presence of the less strongly bondedregions as well as the strongly bonded regions, results in fabric properties which are still not the most desirable.